use strict;
require Exporter;
-require DynaLoader;
use vars qw(@ISA $VERSION $CLASS @EXPORT);
-@ISA = qw(Exporter DynaLoader);
+@ISA = qw(Exporter);
@EXPORT = qw(qv);
-$VERSION = "0.47";
+$VERSION = "0.48";
$CLASS = 'version';
-local $^W; # shut up the 'redefined' warning for UNIVERSAL::VERSION
-bootstrap version if $] < 5.009;
-
# Preloaded methods go here.
1;
-__END__
-
-=head1 NAME
-
-version - Perl extension for Version Objects
-
-=head1 SYNOPSIS
-
- use version;
- $version = version->new("12.2.1"); # must be quoted for Perl < 5.8.1
- print $version; # 12.2.1
- print $version->numify; # 12.002001
- if ( $version gt "12.2" ) # true
-
- $alphaver = version->new("1.02_03"); # must be quoted!
- print $alphaver; # 1.02_030
- print $alphaver->is_alpha(); # true
-
- $ver = qv(1.2); # 1.2.0
- $ver = qv("1.2"); # 1.2.0
-
- $perlver = version->new(5.005_03); # must not be quoted!
- print $perlver; # 5.005030
-
-=head1 DESCRIPTION
-
-Overloaded version objects for all versions of Perl. This module
-implements all of the features of version objects which will be part
-of Perl 5.10.0 except automatic version object creation.
-
-=head2 What IS a version
-
-For the purposes of this module, a version "number" is a sequence of
-positive integral values separated by decimal points and optionally a
-single underscore. This corresponds to what Perl itself uses for a
-version, as well as extending the "version as number" that is discussed
-in the various editions of the Camel book.
-
-There are actually two distinct ways to initialize versions:
-
-=over 4
-
-=item * Numeric Versions
-
-Any initial parameter which "looks like a number", see L<Numeric
-Versions>. This also covers versions with a single decimal place and
-a single embedded underscore, see L<Numeric Alpha Versions>, even though
-these must be quoted to preserve the underscore formatting.
-
-=item * Quoted Versions
-
-Any initial parameter which contains more than one decimal point
-and an optional embedded underscore, see L<Quoted Versions>.
-
-=back
-
-Both of these methods will produce similar version objects, in that
-the default stringification will yield the version L<Normal Form> only
-if required:
-
- $v = version->new(1.002); # 1.002, but compares like 1.2.0
- $v = version->new(1.002003); # 1.002003
- $v2 = version->new( "1.2.3"); # v1.2.3
- $v3 = version->new( 1.2.3); # v1.2.3 for Perl >= 5.8.1
-
-In specific, version numbers initialized as L<Numeric Versions> will
-stringify in Numeric form. Version numbers initialized as L<Quoted Versions>
-will be stringified as L<Normal Form>.
-
-Please see L<Quoting> for more details on how Perl will parse various
-input values.
-
-Any value passed to the new() operator will be parsed only so far as it
-contains a numeric, decimal, or underscore character. So, for example:
-
- $v1 = version->new("99 and 94/100 percent pure"); # $v1 == 99.0
- $v2 = version->new("something"); # $v2 == "" and $v2->numify == 0
-
-However, see L<New Operator> for one case where non-numeric text is
-acceptable when initializing version objects.
-
-=head2 What about v-strings?
-
-Beginning with Perl 5.6.0, an alternate method to code arbitrary strings
-of bytes was introduced, called v-strings. They were intended to be an
-easy way to enter, for example, Unicode strings (which contain two bytes
-per character). Some programs have used them to encode printer control
-characters (e.g. CRLF). They were also intended to be used for $VERSION.
-Their use has been problematic from the start and they will be phased out
-beginning in Perl 5.10.0.
-
-There are two ways to enter v-strings: a bare number with two or more
-decimal places, or a bare number with one or more decimal places and a
-leading 'v' character (also bare). For example:
-
- $vs1 = 1.2.3; # encoded as \1\2\3
- $vs2 = v1.2; # encoded as \1\2
-
-The first of those two syntaxes is destined to be the default way to create
-a version object in 5.10.0, whereas the second will issue a mandatory
-deprecation warning beginning at the same time. In both cases, a v-string
-encoded version will always be stringified in the version L<Normal Form>.
-
-Consequently, the use of v-strings to initialize version objects with
-this module is only possible with Perl 5.8.1 or better (which contain special
-code to enable it). Their use is B<strongly> discouraged in all
-circumstances (especially the leading 'v' style), since the meaning will
-change depending on which Perl you are running. It is better to use
-L<"Quoted Versions"> to ensure the proper interpretation.
-
-=head2 Numeric Versions
-
-These correspond to historical versions of Perl itself prior to 5.6.0,
-as well as all other modules which follow the Camel rules for the
-$VERSION scalar. A numeric version is initialized with what looks like
-a floating point number. Leading zeros B<are> significant and trailing
-zeros are implied so that a minimum of three places is maintained
-between subversions. What this means is that any subversion (digits
-to the right of the decimal place) that contains less than three digits
-will have trailing zeros added to make up the difference, but only for
-purposes of comparison with other version objects. For example:
-
- $v = version->new( 1.2); # prints 1.2, compares as 1.200.0
- $v = version->new( 1.02); # prints 1.02, compares as 1.20.0
- $v = version->new( 1.002); # prints 1.002, compares as 1.2.0
- $v = version->new( 1.0023); # 1.2.300
- $v = version->new( 1.00203); # 1.2.30
- $v = version->new( 1.002_03); # 1.2.30 See "Quoting"
- $v = version->new( 1.002003); # 1.2.3
-
-All of the preceding examples except the second to last are true
-whether or not the input value is quoted. The important feature is that
-the input value contains only a single decimal.
-
-IMPORTANT NOTE: If your numeric version contains more than 3 significant
-digits after the decimal place, it will be split on each multiple of 3, so
-1.0003 becomes 1.0.300, due to the need to remain compatible with Perl's
-own 5.005_03 == 5.5.30 interpretation.
-
-=head2 Quoted Versions
-
-These are the newest form of versions, and correspond to Perl's own
-version style beginning with 5.6.0. Starting with Perl 5.10.0,
-and most likely Perl 6, this is likely to be the preferred form. This
-method requires that the input parameter be quoted, although Perl's after
-5.9.0 can use bare numbers with multiple decimal places as a special form
-of quoting.
-
-Unlike L<Numeric Versions>, Quoted Versions may have more than
-a single decimal point, e.g. "5.6.1" (for all versions of Perl). If a
-Quoted Version has only one decimal place (and no embedded underscore),
-it is interpreted exactly like a L<Numeric Version>.
-
-So, for example:
-
- $v = version->new( "1.002"); # 1.2
- $v = version->new( "1.2.3"); # 1.2.3
- $v = version->new("1.0003"); # 1.0.300
-
-In addition to conventional versions, Quoted Versions can be
-used to create L<Alpha Versions>.
-
-In general, Quoted Versions permit the greatest amount of freedom
-to specify a version, whereas Numeric Versions enforce a certain
-uniformity. See also L<New Operator> for an additional method of
-initializing version objects.
-
-=head2 Numeric Alpha Versions
-
-The one time that a numeric version must be quoted is when a alpha form is
-used with an otherwise numeric version (i.e. a single decimal place). This
-is commonly used for CPAN releases, where CPAN or CPANPLUS will ignore alpha
-versions for automatic updating purposes. Since some developers have used
-only two significant decimal places for their non-alpha releases, the
-version object will automatically take that into account if the initializer
-is quoted. For example Module::Example was released to CPAN with the
-following sequence of $VERSION's:
-
- # $VERSION Stringified
- 0.01 0.010
- 0.02 0.020
- 0.02_01 0.02_0100
- 0.02_02 0.02_0200
- 0.03 0.030
- etc.
-
-As you can see, the version object created from the values in the first
-column may contain a trailing 0, but will otherwise be both mathematically
-equivalent and sorts alpha-numerically as would be expected.
-
-=head2 Object Methods
-
-Overloading has been used with version objects to provide a natural
-interface for their use. All mathematical operations are forbidden,
-since they don't make any sense for base version objects.
-
-=over 4
-
-=item * New Operator
-
-Like all OO interfaces, the new() operator is used to initialize
-version objects. One way to increment versions when programming is to
-use the CVS variable $Revision, which is automatically incremented by
-CVS every time the file is committed to the repository.
-
-In order to facilitate this feature, the following
-code can be employed:
-
- $VERSION = version->new(qw$Revision: 2.7 $);
-
-and the version object will be created as if the following code
-were used:
-
- $VERSION = version->new("v2.7");
-
-In other words, the version will be automatically parsed out of the
-string, and it will be quoted to preserve the meaning CVS normally
-carries for versions. The CVS $Revision$ increments differently from
-numeric versions (i.e. 1.10 follows 1.9), so it must be handled as if
-it were a L<Quoted Version>.
-
-A new version object can be created as a copy of an existing version
-object, either as a class method:
-
- $v1 = version->new(12.3);
- $v2 = version->new($v1);
-
-or as an object method:
-
- $v1 = version->new(12.3);
- $v2 = $v1->new();
-
-and in each case, $v1 and $v2 will be identical.
-
-=back
-
-=over 4
-
-=item * qv()
-
-An alternate way to create a new version object is through the exported
-qv() sub. This is not strictly like other q? operators (like qq, qw),
-in that the only delimiters supported are parentheses (or spaces). It is
-the best way to initialize a short version without triggering the floating
-point interpretation. For example:
-
- $v1 = qv(1.2); # 1.2.0
- $v2 = qv("1.2"); # also 1.2.0
-
-As you can see, either a bare number or a quoted string can be used, and
-either will yield the same version number.
-
-=back
-
-For the subsequent examples, the following three objects will be used:
-
- $ver = version->new("1.2.3.4"); # see "Quoting" below
- $alpha = version->new("1.2.3_4"); # see "Alpha versions" below
- $nver = version->new(1.002); # see "Numeric Versions" above
-
-=over 4
-
-=item * Normal Form
-
-For any version object which is initialized with multiple decimal
-places (either quoted or if possible v-string), or initialized using
-the L<qv()> operator, the stringified representation is returned in
-a normalized or reduced form (no extraneous zeros), and with a leading 'v':
-
- print $ver->normal; # prints as v1.2.3
- print $ver->stringify; # ditto
- print $ver; # ditto
- print $nver->normal; # prints as v1.2.0
- print $nver->stringify; # prints as 1.002, see "Stringification"
-
-In order to preserve the meaning of the processed version, the
-normalized representation will always contain at least three sub terms.
-In other words, the following is guaranteed to always be true:
-
- my $newver = version->new($ver->stringify);
- if ($newver eq $ver ) # always true
- {...}
-
-=back
-
-=over 4
-
-=item * Numification
-
-Although all mathematical operations on version objects are forbidden
-by default, it is possible to retrieve a number which roughly
-corresponds to the version object through the use of the $obj->numify
-method. For formatting purposes, when displaying a number which
-corresponds a version object, all sub versions are assumed to have
-three decimal places. So for example:
-
- print $ver->numify; # prints 1.002003
- print $nver->numify; # prints 1.002
-
-Unlike the stringification operator, there is never any need to append
-trailing zeros to preserve the correct version value.
-
-=back
-
-=over 4
-
-=item * Stringification
-
-In order to mirror as much as possible the existing behavior of ordinary
-$VERSION scalars, the stringification operation will display differently,
-depending on whether the version was initialized as a L<Numeric Version>
-or L<Quoted Version>.
-
-What this means in practice is that if the normal CPAN and Camel rules are
-followed ($VERSION is a floating point number with no more than 3 decimal
-places), the stringified output will be exactly the same as the numified
-output. There will be no visible difference, although the internal
-representation will be different, and the L<Comparison operators> will
-function using the internal coding.
-
-If a version object is initialized using a L<Quoted Version> form, or if
-the number of significant decimal places exceed three, then the stringified
-form will be the L<Normal Form>. The $obj->normal operation can always be
-used to produce the L<Normal Form>, even if the version was originally a
-L<Numeric Version>.
-
- print $ver->stringify; # prints v1.2.3
- print $nver->stringify; # prints 1.002
-
-=back
-
-=over 4
-
-=item * Comparison operators
-
-Both cmp and <=> operators perform the same comparison between terms
-(upgrading to a version object automatically). Perl automatically
-generates all of the other comparison operators based on those two.
-In addition to the obvious equalities listed below, appending a single
-trailing 0 term does not change the value of a version for comparison
-purposes. In other words "v1.2" and "1.2.0" will compare as identical.
-
-For example, the following relations hold:
-
- As Number As String Truth Value
- --------- ------------ -----------
- $ver > 1.0 $ver gt "1.0" true
- $ver < 2.5 $ver lt true
- $ver != 1.3 $ver ne "1.3" true
- $ver == 1.2 $ver eq "1.2" false
- $ver == 1.2.3 $ver eq "1.2.3" see discussion below
-
-It is probably best to chose either the numeric notation or the string
-notation and stick with it, to reduce confusion. Perl6 version objects
-B<may> only support numeric comparisons. See also L<"Quoting">.
-
-WARNING: Comparing version with unequal numbers of decimal places (whether
-explicitly or implicitly initialized), may yield unexpected results at
-first glance. For example, the following inequalities hold:
-
- version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0
- version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0
-
-For this reason, it is best to use either exclusively L<Numeric Versions> or
-L<Quoted Versions> with multiple decimal places.
-
-=back
-
-=over 4
-
-=item * Logical Operators
-
-If you need to test whether a version object
-has been initialized, you can simply test it directly:
-
- $vobj = version->new($something);
- if ( $vobj ) # true only if $something was non-blank
-
-You can also test whether a version object is an L<Alpha version>, for
-example to prevent the use of some feature not present in the main
-release:
-
- $vobj = version->new("1.2_3"); # MUST QUOTE
- ...later...
- if ( $vobj->is_alpha ) # True
-
-=back
-
-=head2 Quoting
-
-Because of the nature of the Perl parsing and tokenizing routines,
-certain initialization values B<must> be quoted in order to correctly
-parse as the intended version, and additionally, some initial values
-B<must not> be quoted to obtain the intended version.
-
-Except for L<Alpha versions>, any version initialized with something
-that looks like a number (a single decimal place) will be parsed in
-the same way whether or not the term is quoted. In order to be
-compatible with earlier Perl version styles, any use of versions of
-the form 5.006001 will be translated as 5.6.1. In other words, a
-version with a single decimal place will be parsed as implicitly
-having three places between subversions.
-
-The complicating factor is that in bare numbers (i.e. unquoted), the
-underscore is a legal numeric character and is automatically stripped
-by the Perl tokenizer before the version code is called. However, if
-a number containing one or more decimals and an underscore is quoted, i.e.
-not bare, that is considered a L<Alpha Version> and the underscore is
-significant.
-
-If you use a mathematic formula that resolves to a floating point number,
-you are dependent on Perl's conversion routines to yield the version you
-expect. You are pretty safe by dividing by a power of 10, for example,
-but other operations are not likely to be what you intend. For example:
-
- $VERSION = version->new((qw$Revision: 1.4)[1]/10);
- print $VERSION; # yields 0.14
- $V2 = version->new(100/9); # Integer overflow in decimal number
- print $V2; # yields something like 11.111.111.100
-
-Perl 5.8.1 and beyond will be able to automatically quote v-strings but
-that is not possible in earlier versions of Perl. In other words:
-
- $version = version->new("v2.5.4"); # legal in all versions of Perl
- $newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1
-
-
-=head2 Types of Versions Objects
-
-There are two types of Version Objects:
-
-=over 4
-
-=item * Ordinary versions
-
-These are the versions that normal modules will use. Can contain as
-many subversions as required. In particular, those using RCS/CVS can
-use the following:
-
- $VERSION = version->new(qw$Revision: 2.7 $);
-
-and the current RCS Revision for that file will be inserted
-automatically. If the file has been moved to a branch, the Revision
-will have three or more elements; otherwise, it will have only two.
-This allows you to automatically increment your module version by
-using the Revision number from the primary file in a distribution, see
-L<ExtUtils::MakeMaker/"VERSION_FROM">.
-
-=item * Alpha Versions
-
-For module authors using CPAN, the convention has been to note
-unstable releases with an underscore in the version string, see
-L<CPAN>. Alpha releases will test as being newer than the more recent
-stable release, and less than the next stable release. For example:
-
- $alphaver = version->new("12.03_01"); # must be quoted
-
-obeys the relationship
-
- 12.03 < $alphaver < 12.04
-
-Alpha versions with a single decimal place will be treated exactly as if
-they were L<Numeric Versions>, for parsing purposes. The stringification for
-alpha versions with a single decimal place may seem surprising, since any
-trailing zeros will visible. For example, the above $alphaver will print as
-
- 12.03_0100
-
-which is mathematically equivalent and ASCII sorts exactly the same as
-without the trailing zeros.
-
-Alpha versions with more than a single decimal place will be treated
-exactly as if they were L<Quoted Versions>, and will display without any
-trailing (or leading) zeros, in the L<Version Normal> form. For example,
-
- $newver = version->new("12.3.1_1");
- print $newver; # v12.3.1_1
-
-=head2 Replacement UNIVERSAL::VERSION
-
-In addition to the version objects, this modules also replaces the core
-UNIVERSAL::VERSION function with one that uses version objects for its
-comparisons. The return from this operator is always the numified form,
-and the warning message generated includes both the numified and normal
-forms (for clarity).
-
-For example:
-
- package Foo;
- $VERSION = 1.2;
-
- package Bar;
- $VERSION = "1.3.5"; # works with all Perl's (since it is quoted)
-
- package main;
- use version;
-
- print $Foo::VERSION; # prints 1.2
-
- print $Bar::VERSION; # prints 1.003005
-
- eval "use CGI 10"; # some far future release
- print $@; # prints "CGI version 10 (10.0.0) required..."
-
-IMPORTANT NOTE: This may mean that code which searches for a specific
-string (to determine whether a given module is available) may need to be
-changed.
-
-The replacement UNIVERSAL::VERSION, when used as a function, like this:
-
- print $module->VERSION;
-
-will also exclusively return the numified form. Technically, the
-$module->VERSION function returns a string (PV) that can be converted to a
-number following the normal Perl rules, when used in a numeric context.
-
-=head1 SUBCLASSING
-
-This module is specifically designed and tested to be easily subclassed.
-In practice, you only need to override the methods you want to change, but
-you have to take some care when overriding new() (since that is where all
-of the parsing takes place). For example, this is a perfect acceptable
-derived class:
-
- package myversion;
- use base version;
- sub new {
- my($self,$n)=@_;
- my $obj;
- # perform any special input handling here
- $obj = $self->SUPER::new($n);
- # and/or add additional hash elements here
- return $obj;
- }
-
-See also L<version::AlphaBeta> on CPAN for an alternate representation of
-version strings.
-
-=head1 EXPORT
-
-qv - quoted version initialization operator
-
-=head1 AUTHOR
-
-John Peacock E<lt>jpeacock@cpan.orgE<gt>
-
-=head1 SEE ALSO
-
-L<perl>.
-
-=cut
--- /dev/null
+=head1 NAME
+
+version - Perl extension for Version Objects
+
+=head1 SYNOPSIS
+
+ use version;
+ $version = version->new("12.2.1"); # must be quoted for Perl < 5.8.1
+ print $version; # 12.2.1
+ print $version->numify; # 12.002001
+ if ( $version gt "12.2" ) # true
+
+ $alphaver = version->new("1.02_03"); # must be quoted!
+ print $alphaver; # 1.02_030
+ print $alphaver->is_alpha(); # true
+
+ $ver = qv(1.2); # 1.2.0
+ $ver = qv("1.2"); # 1.2.0
+
+ $perlver = version->new(5.005_03); # must not be quoted!
+ print $perlver; # 5.005030
+
+=head1 DESCRIPTION
+
+Overloaded version objects for all versions of Perl. This module
+implements all of the features of version objects which will be part
+of Perl 5.10.0 except automatic version object creation.
+
+=head2 What IS a version
+
+For the purposes of this module, a version "number" is a sequence of
+positive integral values separated by decimal points and optionally a
+single underscore. This corresponds to what Perl itself uses for a
+version, as well as extending the "version as number" that is discussed
+in the various editions of the Camel book.
+
+There are actually two distinct ways to initialize versions:
+
+=over 4
+
+=item * Numeric Versions
+
+Any initial parameter which "looks like a number", see L<Numeric
+Versions>. This also covers versions with a single decimal place and
+a single embedded underscore, see L<Numeric Alpha Versions>, even though
+these must be quoted to preserve the underscore formatting.
+
+=item * Quoted Versions
+
+Any initial parameter which contains more than one decimal point
+and an optional embedded underscore, see L<Quoted Versions>.
+
+=back
+
+Both of these methods will produce similar version objects, in that
+the default stringification will yield the version L<Normal Form> only
+if required:
+
+ $v = version->new(1.002); # 1.002, but compares like 1.2.0
+ $v = version->new(1.002003); # 1.002003
+ $v2 = version->new( "1.2.3"); # v1.2.3
+ $v3 = version->new( 1.2.3); # v1.2.3 for Perl >= 5.8.1
+
+In specific, version numbers initialized as L<Numeric Versions> will
+stringify in Numeric form. Version numbers initialized as L<Quoted Versions>
+will be stringified as L<Normal Form>.
+
+Please see L<Quoting> for more details on how Perl will parse various
+input values.
+
+Any value passed to the new() operator will be parsed only so far as it
+contains a numeric, decimal, or underscore character. So, for example:
+
+ $v1 = version->new("99 and 94/100 percent pure"); # $v1 == 99.0
+ $v2 = version->new("something"); # $v2 == "" and $v2->numify == 0
+
+However, see L<New Operator> for one case where non-numeric text is
+acceptable when initializing version objects.
+
+=head2 What about v-strings?
+
+Beginning with Perl 5.6.0, an alternate method to code arbitrary strings
+of bytes was introduced, called v-strings. They were intended to be an
+easy way to enter, for example, Unicode strings (which contain two bytes
+per character). Some programs have used them to encode printer control
+characters (e.g. CRLF). They were also intended to be used for $VERSION.
+Their use has been problematic from the start and they will be phased out
+beginning in Perl 5.10.0.
+
+There are two ways to enter v-strings: a bare number with two or more
+decimal places, or a bare number with one or more decimal places and a
+leading 'v' character (also bare). For example:
+
+ $vs1 = 1.2.3; # encoded as \1\2\3
+ $vs2 = v1.2; # encoded as \1\2
+
+The first of those two syntaxes is destined to be the default way to create
+a version object in 5.10.0, whereas the second will issue a mandatory
+deprecation warning beginning at the same time. In both cases, a v-string
+encoded version will always be stringified in the version L<Normal Form>.
+
+Consequently, the use of v-strings to initialize version objects with
+this module is only possible with Perl 5.8.1 or better (which contain special
+code to enable it). Their use is B<strongly> discouraged in all
+circumstances (especially the leading 'v' style), since the meaning will
+change depending on which Perl you are running. It is better to use
+L<"Quoted Versions"> to ensure the proper interpretation.
+
+=head2 Numeric Versions
+
+These correspond to historical versions of Perl itself prior to 5.6.0,
+as well as all other modules which follow the Camel rules for the
+$VERSION scalar. A numeric version is initialized with what looks like
+a floating point number. Leading zeros B<are> significant and trailing
+zeros are implied so that a minimum of three places is maintained
+between subversions. What this means is that any subversion (digits
+to the right of the decimal place) that contains less than three digits
+will have trailing zeros added to make up the difference, but only for
+purposes of comparison with other version objects. For example:
+
+ $v = version->new( 1.2); # prints 1.2, compares as 1.200.0
+ $v = version->new( 1.02); # prints 1.02, compares as 1.20.0
+ $v = version->new( 1.002); # prints 1.002, compares as 1.2.0
+ $v = version->new( 1.0023); # 1.2.300
+ $v = version->new( 1.00203); # 1.2.30
+ $v = version->new( 1.002_03); # 1.2.30 See "Quoting"
+ $v = version->new( 1.002003); # 1.2.3
+
+All of the preceding examples except the second to last are true
+whether or not the input value is quoted. The important feature is that
+the input value contains only a single decimal.
+
+IMPORTANT NOTE: If your numeric version contains more than 3 significant
+digits after the decimal place, it will be split on each multiple of 3, so
+1.0003 becomes 1.0.300, due to the need to remain compatible with Perl's
+own 5.005_03 == 5.5.30 interpretation.
+
+=head2 Quoted Versions
+
+These are the newest form of versions, and correspond to Perl's own
+version style beginning with 5.6.0. Starting with Perl 5.10.0,
+and most likely Perl 6, this is likely to be the preferred form. This
+method requires that the input parameter be quoted, although Perl's after
+5.9.0 can use bare numbers with multiple decimal places as a special form
+of quoting.
+
+Unlike L<Numeric Versions>, Quoted Versions may have more than
+a single decimal point, e.g. "5.6.1" (for all versions of Perl). If a
+Quoted Version has only one decimal place (and no embedded underscore),
+it is interpreted exactly like a L<Numeric Version>.
+
+So, for example:
+
+ $v = version->new( "1.002"); # 1.2
+ $v = version->new( "1.2.3"); # 1.2.3
+ $v = version->new("1.0003"); # 1.0.300
+
+In addition to conventional versions, Quoted Versions can be
+used to create L<Alpha Versions>.
+
+In general, Quoted Versions permit the greatest amount of freedom
+to specify a version, whereas Numeric Versions enforce a certain
+uniformity. See also L<New Operator> for an additional method of
+initializing version objects.
+
+=head2 Numeric Alpha Versions
+
+The one time that a numeric version must be quoted is when a alpha form is
+used with an otherwise numeric version (i.e. a single decimal place). This
+is commonly used for CPAN releases, where CPAN or CPANPLUS will ignore alpha
+versions for automatic updating purposes. Since some developers have used
+only two significant decimal places for their non-alpha releases, the
+version object will automatically take that into account if the initializer
+is quoted. For example Module::Example was released to CPAN with the
+following sequence of $VERSION's:
+
+ # $VERSION Stringified
+ 0.01 0.010
+ 0.02 0.020
+ 0.02_01 0.02_0100
+ 0.02_02 0.02_0200
+ 0.03 0.030
+ etc.
+
+As you can see, the version object created from the values in the first
+column may contain a trailing 0, but will otherwise be both mathematically
+equivalent and sorts alpha-numerically as would be expected.
+
+=head2 Object Methods
+
+Overloading has been used with version objects to provide a natural
+interface for their use. All mathematical operations are forbidden,
+since they don't make any sense for base version objects.
+
+=over 4
+
+=item * New Operator
+
+Like all OO interfaces, the new() operator is used to initialize
+version objects. One way to increment versions when programming is to
+use the CVS variable $Revision, which is automatically incremented by
+CVS every time the file is committed to the repository.
+
+In order to facilitate this feature, the following
+code can be employed:
+
+ $VERSION = version->new(qw$Revision: 2.7 $);
+
+and the version object will be created as if the following code
+were used:
+
+ $VERSION = version->new("v2.7");
+
+In other words, the version will be automatically parsed out of the
+string, and it will be quoted to preserve the meaning CVS normally
+carries for versions. The CVS $Revision$ increments differently from
+numeric versions (i.e. 1.10 follows 1.9), so it must be handled as if
+it were a L<Quoted Version>.
+
+A new version object can be created as a copy of an existing version
+object, either as a class method:
+
+ $v1 = version->new(12.3);
+ $v2 = version->new($v1);
+
+or as an object method:
+
+ $v1 = version->new(12.3);
+ $v2 = $v1->new();
+
+and in each case, $v1 and $v2 will be identical.
+
+=back
+
+=over 4
+
+=item * qv()
+
+An alternate way to create a new version object is through the exported
+qv() sub. This is not strictly like other q? operators (like qq, qw),
+in that the only delimiters supported are parentheses (or spaces). It is
+the best way to initialize a short version without triggering the floating
+point interpretation. For example:
+
+ $v1 = qv(1.2); # 1.2.0
+ $v2 = qv("1.2"); # also 1.2.0
+
+As you can see, either a bare number or a quoted string can be used, and
+either will yield the same version number.
+
+=back
+
+For the subsequent examples, the following three objects will be used:
+
+ $ver = version->new("1.2.3.4"); # see "Quoting" below
+ $alpha = version->new("1.2.3_4"); # see "Alpha versions" below
+ $nver = version->new(1.002); # see "Numeric Versions" above
+
+=over 4
+
+=item * Normal Form
+
+For any version object which is initialized with multiple decimal
+places (either quoted or if possible v-string), or initialized using
+the L<qv()> operator, the stringified representation is returned in
+a normalized or reduced form (no extraneous zeros), and with a leading 'v':
+
+ print $ver->normal; # prints as v1.2.3
+ print $ver->stringify; # ditto
+ print $ver; # ditto
+ print $nver->normal; # prints as v1.2.0
+ print $nver->stringify; # prints as 1.002, see "Stringification"
+
+In order to preserve the meaning of the processed version, the
+normalized representation will always contain at least three sub terms.
+In other words, the following is guaranteed to always be true:
+
+ my $newver = version->new($ver->stringify);
+ if ($newver eq $ver ) # always true
+ {...}
+
+=back
+
+=over 4
+
+=item * Numification
+
+Although all mathematical operations on version objects are forbidden
+by default, it is possible to retrieve a number which roughly
+corresponds to the version object through the use of the $obj->numify
+method. For formatting purposes, when displaying a number which
+corresponds a version object, all sub versions are assumed to have
+three decimal places. So for example:
+
+ print $ver->numify; # prints 1.002003
+ print $nver->numify; # prints 1.002
+
+Unlike the stringification operator, there is never any need to append
+trailing zeros to preserve the correct version value.
+
+=back
+
+=over 4
+
+=item * Stringification
+
+In order to mirror as much as possible the existing behavior of ordinary
+$VERSION scalars, the stringification operation will display differently,
+depending on whether the version was initialized as a L<Numeric Version>
+or L<Quoted Version>.
+
+What this means in practice is that if the normal CPAN and Camel rules are
+followed ($VERSION is a floating point number with no more than 3 decimal
+places), the stringified output will be exactly the same as the numified
+output. There will be no visible difference, although the internal
+representation will be different, and the L<Comparison operators> will
+function using the internal coding.
+
+If a version object is initialized using a L<Quoted Version> form, or if
+the number of significant decimal places exceed three, then the stringified
+form will be the L<Normal Form>. The $obj->normal operation can always be
+used to produce the L<Normal Form>, even if the version was originally a
+L<Numeric Version>.
+
+ print $ver->stringify; # prints v1.2.3
+ print $nver->stringify; # prints 1.002
+
+=back
+
+=over 4
+
+=item * Comparison operators
+
+Both cmp and <=> operators perform the same comparison between terms
+(upgrading to a version object automatically). Perl automatically
+generates all of the other comparison operators based on those two.
+In addition to the obvious equalities listed below, appending a single
+trailing 0 term does not change the value of a version for comparison
+purposes. In other words "v1.2" and "1.2.0" will compare as identical.
+
+For example, the following relations hold:
+
+ As Number As String Truth Value
+ --------- ------------ -----------
+ $ver > 1.0 $ver gt "1.0" true
+ $ver < 2.5 $ver lt true
+ $ver != 1.3 $ver ne "1.3" true
+ $ver == 1.2 $ver eq "1.2" false
+ $ver == 1.2.3 $ver eq "1.2.3" see discussion below
+
+It is probably best to chose either the numeric notation or the string
+notation and stick with it, to reduce confusion. Perl6 version objects
+B<may> only support numeric comparisons. See also L<"Quoting">.
+
+WARNING: Comparing version with unequal numbers of decimal places (whether
+explicitly or implicitly initialized), may yield unexpected results at
+first glance. For example, the following inequalities hold:
+
+ version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0
+ version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0
+
+For this reason, it is best to use either exclusively L<Numeric Versions> or
+L<Quoted Versions> with multiple decimal places.
+
+=back
+
+=over 4
+
+=item * Logical Operators
+
+If you need to test whether a version object
+has been initialized, you can simply test it directly:
+
+ $vobj = version->new($something);
+ if ( $vobj ) # true only if $something was non-blank
+
+You can also test whether a version object is an L<Alpha version>, for
+example to prevent the use of some feature not present in the main
+release:
+
+ $vobj = version->new("1.2_3"); # MUST QUOTE
+ ...later...
+ if ( $vobj->is_alpha ) # True
+
+=back
+
+=head2 Quoting
+
+Because of the nature of the Perl parsing and tokenizing routines,
+certain initialization values B<must> be quoted in order to correctly
+parse as the intended version, and additionally, some initial values
+B<must not> be quoted to obtain the intended version.
+
+Except for L<Alpha versions>, any version initialized with something
+that looks like a number (a single decimal place) will be parsed in
+the same way whether or not the term is quoted. In order to be
+compatible with earlier Perl version styles, any use of versions of
+the form 5.006001 will be translated as 5.6.1. In other words, a
+version with a single decimal place will be parsed as implicitly
+having three places between subversions.
+
+The complicating factor is that in bare numbers (i.e. unquoted), the
+underscore is a legal numeric character and is automatically stripped
+by the Perl tokenizer before the version code is called. However, if
+a number containing one or more decimals and an underscore is quoted, i.e.
+not bare, that is considered a L<Alpha Version> and the underscore is
+significant.
+
+If you use a mathematic formula that resolves to a floating point number,
+you are dependent on Perl's conversion routines to yield the version you
+expect. You are pretty safe by dividing by a power of 10, for example,
+but other operations are not likely to be what you intend. For example:
+
+ $VERSION = version->new((qw$Revision: 1.4)[1]/10);
+ print $VERSION; # yields 0.14
+ $V2 = version->new(100/9); # Integer overflow in decimal number
+ print $V2; # yields something like 11.111.111.100
+
+Perl 5.8.1 and beyond will be able to automatically quote v-strings but
+that is not possible in earlier versions of Perl. In other words:
+
+ $version = version->new("v2.5.4"); # legal in all versions of Perl
+ $newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1
+
+
+=head2 Types of Versions Objects
+
+There are two types of Version Objects:
+
+=over 4
+
+=item * Ordinary versions
+
+These are the versions that normal modules will use. Can contain as
+many subversions as required. In particular, those using RCS/CVS can
+use the following:
+
+ $VERSION = version->new(qw$Revision: 2.7 $);
+
+and the current RCS Revision for that file will be inserted
+automatically. If the file has been moved to a branch, the Revision
+will have three or more elements; otherwise, it will have only two.
+This allows you to automatically increment your module version by
+using the Revision number from the primary file in a distribution, see
+L<ExtUtils::MakeMaker/"VERSION_FROM">.
+
+=item * Alpha Versions
+
+For module authors using CPAN, the convention has been to note
+unstable releases with an underscore in the version string, see
+L<CPAN>. Alpha releases will test as being newer than the more recent
+stable release, and less than the next stable release. For example:
+
+ $alphaver = version->new("12.03_01"); # must be quoted
+
+obeys the relationship
+
+ 12.03 < $alphaver < 12.04
+
+Alpha versions with a single decimal place will be treated exactly as if
+they were L<Numeric Versions>, for parsing purposes. The stringification for
+alpha versions with a single decimal place may seem surprising, since any
+trailing zeros will visible. For example, the above $alphaver will print as
+
+ 12.03_0100
+
+which is mathematically equivalent and ASCII sorts exactly the same as
+without the trailing zeros.
+
+Alpha versions with more than a single decimal place will be treated
+exactly as if they were L<Quoted Versions>, and will display without any
+trailing (or leading) zeros, in the L<Version Normal> form. For example,
+
+ $newver = version->new("12.3.1_1");
+ print $newver; # v12.3.1_1
+
+=head2 Replacement UNIVERSAL::VERSION
+
+In addition to the version objects, this modules also replaces the core
+UNIVERSAL::VERSION function with one that uses version objects for its
+comparisons. The return from this operator is always the numified form,
+and the warning message generated includes both the numified and normal
+forms (for clarity).
+
+For example:
+
+ package Foo;
+ $VERSION = 1.2;
+
+ package Bar;
+ $VERSION = "1.3.5"; # works with all Perl's (since it is quoted)
+
+ package main;
+ use version;
+
+ print $Foo::VERSION; # prints 1.2
+
+ print $Bar::VERSION; # prints 1.003005
+
+ eval "use CGI 10"; # some far future release
+ print $@; # prints "CGI version 10 (10.0.0) required..."
+
+IMPORTANT NOTE: This may mean that code which searches for a specific
+string (to determine whether a given module is available) may need to be
+changed.
+
+The replacement UNIVERSAL::VERSION, when used as a function, like this:
+
+ print $module->VERSION;
+
+will also exclusively return the numified form. Technically, the
+$module->VERSION function returns a string (PV) that can be converted to a
+number following the normal Perl rules, when used in a numeric context.
+
+=head1 SUBCLASSING
+
+This module is specifically designed and tested to be easily subclassed.
+In practice, you only need to override the methods you want to change, but
+you have to take some care when overriding new() (since that is where all
+of the parsing takes place). For example, this is a perfect acceptable
+derived class:
+
+ package myversion;
+ use base version;
+ sub new {
+ my($self,$n)=@_;
+ my $obj;
+ # perform any special input handling here
+ $obj = $self->SUPER::new($n);
+ # and/or add additional hash elements here
+ return $obj;
+ }
+
+See also L<version::AlphaBeta> on CPAN for an alternate representation of
+version strings.
+
+=head1 EXPORT
+
+qv - quoted version initialization operator
+
+=head1 AUTHOR
+
+John Peacock E<lt>jpeacock@cpan.orgE<gt>
+
+=head1 SEE ALSO
+
+L<perl>.
+
+=cut
+=head1 NAME
+
+version - Perl extension for Version Objects
+
+=head1 SYNOPSIS
+
+ use version;
+ $version = version->new("12.2.1"); # must be quoted for Perl < 5.8.1
+ print $version; # 12.2.1
+ print $version->numify; # 12.002001
+ if ( $version gt "12.2" ) # true
+
+ $alphaver = version->new("1.02_03"); # must be quoted!
+ print $alphaver; # 1.02_030
+ print $alphaver->is_alpha(); # true
+
+ $ver = qv(1.2); # 1.2.0
+ $ver = qv("1.2"); # 1.2.0
+
+ $perlver = version->new(5.005_03); # must not be quoted!
+ print $perlver; # 5.005030
+
+=head1 DESCRIPTION
+
+Overloaded version objects for all versions of Perl. This module
+implements all of the features of version objects which will be part
+of Perl 5.10.0 except automatic version object creation.
+
+=head2 What IS a version
+
+For the purposes of this module, a version "number" is a sequence of
+positive integral values separated by decimal points and optionally a
+single underscore. This corresponds to what Perl itself uses for a
+version, as well as extending the "version as number" that is discussed
+in the various editions of the Camel book.
+
+There are actually two distinct ways to initialize versions:
+
+=over 4
+
+=item * Numeric Versions
+
+Any initial parameter which "looks like a number", see L<Numeric
+Versions>. This also covers versions with a single decimal place and
+a single embedded underscore, see L<Numeric Alpha Versions>, even though
+these must be quoted to preserve the underscore formatting.
+
+=item * Quoted Versions
+
+Any initial parameter which contains more than one decimal point
+and an optional embedded underscore, see L<Quoted Versions>.
+
+=back
+
+Both of these methods will produce similar version objects, in that
+the default stringification will yield the version L<Normal Form> only
+if required:
+
+ $v = version->new(1.002); # 1.002, but compares like 1.2.0
+ $v = version->new(1.002003); # 1.002003
+ $v2 = version->new( "1.2.3"); # v1.2.3
+ $v3 = version->new( 1.2.3); # v1.2.3 for Perl >= 5.8.1
+
+In specific, version numbers initialized as L<Numeric Versions> will
+stringify in Numeric form. Version numbers initialized as L<Quoted Versions>
+will be stringified as L<Normal Form>.
+
+Please see L<Quoting> for more details on how Perl will parse various
+input values.
+
+Any value passed to the new() operator will be parsed only so far as it
+contains a numeric, decimal, or underscore character. So, for example:
+
+ $v1 = version->new("99 and 94/100 percent pure"); # $v1 == 99.0
+ $v2 = version->new("something"); # $v2 == "" and $v2->numify == 0
+
+However, see L<New Operator> for one case where non-numeric text is
+acceptable when initializing version objects.
+
+=head2 What about v-strings?
+
+Beginning with Perl 5.6.0, an alternate method to code arbitrary strings
+of bytes was introduced, called v-strings. They were intended to be an
+easy way to enter, for example, Unicode strings (which contain two bytes
+per character). Some programs have used them to encode printer control
+characters (e.g. CRLF). They were also intended to be used for $VERSION.
+Their use has been problematic from the start and they will be phased out
+beginning in Perl 5.10.0.
+
+There are two ways to enter v-strings: a bare number with two or more
+decimal places, or a bare number with one or more decimal places and a
+leading 'v' character (also bare). For example:
+
+ $vs1 = 1.2.3; # encoded as \1\2\3
+ $vs2 = v1.2; # encoded as \1\2
+
+The first of those two syntaxes is destined to be the default way to create
+a version object in 5.10.0, whereas the second will issue a mandatory
+deprecation warning beginning at the same time. In both cases, a v-string
+encoded version will always be stringified in the version L<Normal Form>.
+
+Consequently, the use of v-strings to initialize version objects with
+this module is only possible with Perl 5.8.1 or better (which contain special
+code to enable it). Their use is B<strongly> discouraged in all
+circumstances (especially the leading 'v' style), since the meaning will
+change depending on which Perl you are running. It is better to use
+L<"Quoted Versions"> to ensure the proper interpretation.
+
+=head2 Numeric Versions
+
+These correspond to historical versions of Perl itself prior to 5.6.0,
+as well as all other modules which follow the Camel rules for the
+$VERSION scalar. A numeric version is initialized with what looks like
+a floating point number. Leading zeros B<are> significant and trailing
+zeros are implied so that a minimum of three places is maintained
+between subversions. What this means is that any subversion (digits
+to the right of the decimal place) that contains less than three digits
+will have trailing zeros added to make up the difference, but only for
+purposes of comparison with other version objects. For example:
+
+ $v = version->new( 1.2); # prints 1.2, compares as 1.200.0
+ $v = version->new( 1.02); # prints 1.02, compares as 1.20.0
+ $v = version->new( 1.002); # prints 1.002, compares as 1.2.0
+ $v = version->new( 1.0023); # 1.2.300
+ $v = version->new( 1.00203); # 1.2.30
+ $v = version->new( 1.002_03); # 1.2.30 See "Quoting"
+ $v = version->new( 1.002003); # 1.2.3
+
+All of the preceding examples except the second to last are true
+whether or not the input value is quoted. The important feature is that
+the input value contains only a single decimal.
+
+IMPORTANT NOTE: If your numeric version contains more than 3 significant
+digits after the decimal place, it will be split on each multiple of 3, so
+1.0003 becomes 1.0.300, due to the need to remain compatible with Perl's
+own 5.005_03 == 5.5.30 interpretation.
+
+=head2 Quoted Versions
+
+These are the newest form of versions, and correspond to Perl's own
+version style beginning with 5.6.0. Starting with Perl 5.10.0,
+and most likely Perl 6, this is likely to be the preferred form. This
+method requires that the input parameter be quoted, although Perl's after
+5.9.0 can use bare numbers with multiple decimal places as a special form
+of quoting.
+
+Unlike L<Numeric Versions>, Quoted Versions may have more than
+a single decimal point, e.g. "5.6.1" (for all versions of Perl). If a
+Quoted Version has only one decimal place (and no embedded underscore),
+it is interpreted exactly like a L<Numeric Version>.
+
+So, for example:
+
+ $v = version->new( "1.002"); # 1.2
+ $v = version->new( "1.2.3"); # 1.2.3
+ $v = version->new("1.0003"); # 1.0.300
+
+In addition to conventional versions, Quoted Versions can be
+used to create L<Alpha Versions>.
+
+In general, Quoted Versions permit the greatest amount of freedom
+to specify a version, whereas Numeric Versions enforce a certain
+uniformity. See also L<New Operator> for an additional method of
+initializing version objects.
+
+=head2 Numeric Alpha Versions
+
+The one time that a numeric version must be quoted is when a alpha form is
+used with an otherwise numeric version (i.e. a single decimal place). This
+is commonly used for CPAN releases, where CPAN or CPANPLUS will ignore alpha
+versions for automatic updating purposes. Since some developers have used
+only two significant decimal places for their non-alpha releases, the
+version object will automatically take that into account if the initializer
+is quoted. For example Module::Example was released to CPAN with the
+following sequence of $VERSION's:
+
+ # $VERSION Stringified
+ 0.01 0.010
+ 0.02 0.020
+ 0.02_01 0.02_0100
+ 0.02_02 0.02_0200
+ 0.03 0.030
+ etc.
+
+As you can see, the version object created from the values in the first
+column may contain a trailing 0, but will otherwise be both mathematically
+equivalent and sorts alpha-numerically as would be expected.
+
+=head2 Object Methods
+
+Overloading has been used with version objects to provide a natural
+interface for their use. All mathematical operations are forbidden,
+since they don't make any sense for base version objects.
+
+=over 4
+
+=item * New Operator
+
+Like all OO interfaces, the new() operator is used to initialize
+version objects. One way to increment versions when programming is to
+use the CVS variable $Revision, which is automatically incremented by
+CVS every time the file is committed to the repository.
+
+In order to facilitate this feature, the following
+code can be employed:
+
+ $VERSION = version->new(qw$Revision: 2.7 $);
+
+and the version object will be created as if the following code
+were used:
+
+ $VERSION = version->new("v2.7");
+
+In other words, the version will be automatically parsed out of the
+string, and it will be quoted to preserve the meaning CVS normally
+carries for versions. The CVS $Revision$ increments differently from
+numeric versions (i.e. 1.10 follows 1.9), so it must be handled as if
+it were a L<Quoted Version>.
+
+A new version object can be created as a copy of an existing version
+object, either as a class method:
+
+ $v1 = version->new(12.3);
+ $v2 = version->new($v1);
+
+or as an object method:
+
+ $v1 = version->new(12.3);
+ $v2 = $v1->new();
+
+and in each case, $v1 and $v2 will be identical.
+
+=back
+
+=over 4
+
+=item * qv()
+
+An alternate way to create a new version object is through the exported
+qv() sub. This is not strictly like other q? operators (like qq, qw),
+in that the only delimiters supported are parentheses (or spaces). It is
+the best way to initialize a short version without triggering the floating
+point interpretation. For example:
+
+ $v1 = qv(1.2); # 1.2.0
+ $v2 = qv("1.2"); # also 1.2.0
+
+As you can see, either a bare number or a quoted string can be used, and
+either will yield the same version number.
+
+=back
+
+For the subsequent examples, the following three objects will be used:
+
+ $ver = version->new("1.2.3.4"); # see "Quoting" below
+ $alpha = version->new("1.2.3_4"); # see "Alpha versions" below
+ $nver = version->new(1.002); # see "Numeric Versions" above
+
+=over 4
+
+=item * Normal Form
+
+For any version object which is initialized with multiple decimal
+places (either quoted or if possible v-string), or initialized using
+the L<qv()> operator, the stringified representation is returned in
+a normalized or reduced form (no extraneous zeros), and with a leading 'v':
+
+ print $ver->normal; # prints as v1.2.3
+ print $ver->stringify; # ditto
+ print $ver; # ditto
+ print $nver->normal; # prints as v1.2.0
+ print $nver->stringify; # prints as 1.002, see "Stringification"
+
+In order to preserve the meaning of the processed version, the
+normalized representation will always contain at least three sub terms.
+In other words, the following is guaranteed to always be true:
+
+ my $newver = version->new($ver->stringify);
+ if ($newver eq $ver ) # always true
+ {...}
+
+=back
+
+=over 4
+
+=item * Numification
+
+Although all mathematical operations on version objects are forbidden
+by default, it is possible to retrieve a number which roughly
+corresponds to the version object through the use of the $obj->numify
+method. For formatting purposes, when displaying a number which
+corresponds a version object, all sub versions are assumed to have
+three decimal places. So for example:
+
+ print $ver->numify; # prints 1.002003
+ print $nver->numify; # prints 1.002
+
+Unlike the stringification operator, there is never any need to append
+trailing zeros to preserve the correct version value.
+
+=back
+
+=over 4
+
+=item * Stringification
+
+In order to mirror as much as possible the existing behavior of ordinary
+$VERSION scalars, the stringification operation will display differently,
+depending on whether the version was initialized as a L<Numeric Version>
+or L<Quoted Version>.
+
+What this means in practice is that if the normal CPAN and Camel rules are
+followed ($VERSION is a floating point number with no more than 3 decimal
+places), the stringified output will be exactly the same as the numified
+output. There will be no visible difference, although the internal
+representation will be different, and the L<Comparison operators> will
+function using the internal coding.
+
+If a version object is initialized using a L<Quoted Version> form, or if
+the number of significant decimal places exceed three, then the stringified
+form will be the L<Normal Form>. The $obj->normal operation can always be
+used to produce the L<Normal Form>, even if the version was originally a
+L<Numeric Version>.
+
+ print $ver->stringify; # prints v1.2.3
+ print $nver->stringify; # prints 1.002
+
+=back
+
+=over 4
+
+=item * Comparison operators
+
+Both cmp and <=> operators perform the same comparison between terms
+(upgrading to a version object automatically). Perl automatically
+generates all of the other comparison operators based on those two.
+In addition to the obvious equalities listed below, appending a single
+trailing 0 term does not change the value of a version for comparison
+purposes. In other words "v1.2" and "1.2.0" will compare as identical.
+
+For example, the following relations hold:
+
+ As Number As String Truth Value
+ --------- ------------ -----------
+ $ver > 1.0 $ver gt "1.0" true
+ $ver < 2.5 $ver lt true
+ $ver != 1.3 $ver ne "1.3" true
+ $ver == 1.2 $ver eq "1.2" false
+ $ver == 1.2.3 $ver eq "1.2.3" see discussion below
+
+It is probably best to chose either the numeric notation or the string
+notation and stick with it, to reduce confusion. Perl6 version objects
+B<may> only support numeric comparisons. See also L<"Quoting">.
+
+WARNING: Comparing version with unequal numbers of decimal places (whether
+explicitly or implicitly initialized), may yield unexpected results at
+first glance. For example, the following inequalities hold:
+
+ version->new(0.96) > version->new(0.95); # 0.960.0 > 0.950.0
+ version->new("0.96.1") < version->new(0.95); # 0.096.1 < 0.950.0
+
+For this reason, it is best to use either exclusively L<Numeric Versions> or
+L<Quoted Versions> with multiple decimal places.
+
+=back
+
+=over 4
+
+=item * Logical Operators
+
+If you need to test whether a version object
+has been initialized, you can simply test it directly:
+
+ $vobj = version->new($something);
+ if ( $vobj ) # true only if $something was non-blank
+
+You can also test whether a version object is an L<Alpha version>, for
+example to prevent the use of some feature not present in the main
+release:
+
+ $vobj = version->new("1.2_3"); # MUST QUOTE
+ ...later...
+ if ( $vobj->is_alpha ) # True
+
+=back
+
+=head2 Quoting
+
+Because of the nature of the Perl parsing and tokenizing routines,
+certain initialization values B<must> be quoted in order to correctly
+parse as the intended version, and additionally, some initial values
+B<must not> be quoted to obtain the intended version.
+
+Except for L<Alpha versions>, any version initialized with something
+that looks like a number (a single decimal place) will be parsed in
+the same way whether or not the term is quoted. In order to be
+compatible with earlier Perl version styles, any use of versions of
+the form 5.006001 will be translated as 5.6.1. In other words, a
+version with a single decimal place will be parsed as implicitly
+having three places between subversions.
+
+The complicating factor is that in bare numbers (i.e. unquoted), the
+underscore is a legal numeric character and is automatically stripped
+by the Perl tokenizer before the version code is called. However, if
+a number containing one or more decimals and an underscore is quoted, i.e.
+not bare, that is considered a L<Alpha Version> and the underscore is
+significant.
+
+If you use a mathematic formula that resolves to a floating point number,
+you are dependent on Perl's conversion routines to yield the version you
+expect. You are pretty safe by dividing by a power of 10, for example,
+but other operations are not likely to be what you intend. For example:
+
+ $VERSION = version->new((qw$Revision: 1.4)[1]/10);
+ print $VERSION; # yields 0.14
+ $V2 = version->new(100/9); # Integer overflow in decimal number
+ print $V2; # yields something like 11.111.111.100
+
+Perl 5.8.1 and beyond will be able to automatically quote v-strings but
+that is not possible in earlier versions of Perl. In other words:
+
+ $version = version->new("v2.5.4"); # legal in all versions of Perl
+ $newvers = version->new(v2.5.4); # legal only in Perl >= 5.8.1
+
+
+=head2 Types of Versions Objects
+
+There are two types of Version Objects:
+
+=over 4
+
+=item * Ordinary versions
+
+These are the versions that normal modules will use. Can contain as
+many subversions as required. In particular, those using RCS/CVS can
+use the following:
+
+ $VERSION = version->new(qw$Revision: 2.7 $);
+
+and the current RCS Revision for that file will be inserted
+automatically. If the file has been moved to a branch, the Revision
+will have three or more elements; otherwise, it will have only two.
+This allows you to automatically increment your module version by
+using the Revision number from the primary file in a distribution, see
+L<ExtUtils::MakeMaker/"VERSION_FROM">.
+
+=item * Alpha Versions
+
+For module authors using CPAN, the convention has been to note
+unstable releases with an underscore in the version string, see
+L<CPAN>. Alpha releases will test as being newer than the more recent
+stable release, and less than the next stable release. For example:
+
+ $alphaver = version->new("12.03_01"); # must be quoted
+
+obeys the relationship
+
+ 12.03 < $alphaver < 12.04
+
+Alpha versions with a single decimal place will be treated exactly as if
+they were L<Numeric Versions>, for parsing purposes. The stringification for
+alpha versions with a single decimal place may seem surprising, since any
+trailing zeros will visible. For example, the above $alphaver will print as
+
+ 12.03_0100
+
+which is mathematically equivalent and ASCII sorts exactly the same as
+without the trailing zeros.
+
+Alpha versions with more than a single decimal place will be treated
+exactly as if they were L<Quoted Versions>, and will display without any
+trailing (or leading) zeros, in the L<Version Normal> form. For example,
+
+ $newver = version->new("12.3.1_1");
+ print $newver; # v12.3.1_1
+
+=head2 Replacement UNIVERSAL::VERSION
+
+In addition to the version objects, this modules also replaces the core
+UNIVERSAL::VERSION function with one that uses version objects for its
+comparisons. The return from this operator is always the numified form,
+and the warning message generated includes both the numified and normal
+forms (for clarity).
+
+For example:
+
+ package Foo;
+ $VERSION = 1.2;
+
+ package Bar;
+ $VERSION = "1.3.5"; # works with all Perl's (since it is quoted)
+
+ package main;
+ use version;
+
+ print $Foo::VERSION; # prints 1.2
+
+ print $Bar::VERSION; # prints 1.003005
+
+ eval "use CGI 10"; # some far future release
+ print $@; # prints "CGI version 10 (10.0.0) required..."
+
+IMPORTANT NOTE: This may mean that code which searches for a specific
+string (to determine whether a given module is available) may need to be
+changed.
+
+The replacement UNIVERSAL::VERSION, when used as a function, like this:
+
+ print $module->VERSION;
+
+will also exclusively return the numified form. Technically, the
+$module->VERSION function returns a string (PV) that can be converted to a
+number following the normal Perl rules, when used in a numeric context.
+
+=head1 SUBCLASSING
+
+This module is specifically designed and tested to be easily subclassed.
+In practice, you only need to override the methods you want to change, but
+you have to take some care when overriding new() (since that is where all
+of the parsing takes place). For example, this is a perfect acceptable
+derived class:
+
+ package myversion;
+ use base version;
+ sub new {
+ my($self,$n)=@_;
+ my $obj;
+ # perform any special input handling here
+ $obj = $self->SUPER::new($n);
+ # and/or add additional hash elements here
+ return $obj;
+ }
+
+See also L<version::AlphaBeta> on CPAN for an alternate representation of
+version strings.
+
+=head1 EXPORT
+
+qv - quoted version initialization operator
+
+=head1 AUTHOR
+
+John Peacock E<lt>jpeacock@cpan.orgE<gt>
+
+=head1 SEE ALSO
+
+L<perl>.
+
+=cut
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